126 



VERTEBRATA : MAMMALIA. 

 FIG. 142. 



-, 

 - V - 



--*'!:-- r^:" - ' ? 



American Beaver, Castor canudensis, Kuhl. 



themselves ; the lower is beneath the water, and contains 

 their stores of bark and roots. The only opening to the 

 hut is beneath the water. They have burrows in the 

 banks, whither they retire when their houses are attacked. 

 The general color of the beaver is a uniform reddish- 

 brown, and the fur is of excellent quality. Our only 

 living species (Fig. 142), is about two feet in length ; a 

 fossil species is more than twice as large. 



The true Squirrels (Sciurus), the Flying Squirrels (Pter- 

 omys), the Striped Squirrels (Tawias), the Gophers and 

 Spermophiles (Spermophilus), and the Prairie Dogs (Cyn- 

 omys], are rodents which are included in the Squirrel 

 family or Sciuridae. In this family are also included the 

 Marmots and Woodchucks (Arctomys). 



The typical Squirrels (Sciurus), are the most graceful 

 and beautiful of all the Kodents. They have compressed 

 incisors, rather long ears, divided lip, and they are des- 

 titute of cheek pouches. The true Squirrels and Flying 

 Squirrels live upon trees; the others in the ground. 



The Porcupines or Hystricidae are conspicuous among 



